tty: Fix regressions caused by commit b50989dc

The following commit made console open fails while booting:

	commit b50989dc444599c8b21edc23536fc305f4e9b7d5
	Author: Alan Cox <alan@linux.intel.com>
	Date:   Sat Sep 19 13:13:22 2009 -0700

	tty: make the kref destructor occur asynchronously

Due to tty release routines run in a workqueue now, error like the
following will be reported while booting:

INIT open /dev/console Input/output error

It also causes hibernation regression to appear as reported at
http://bugzilla.kernel.org/show_bug.cgi?id=14229

The reason is that now there's latency issue with closing, but when
we open a "closing not finished" tty, -EIO will be returned.

Fix it as per the following Alan's suggestion:

  Fun but it's actually not a bug and the fix is wrong in itself as
  the port may be closing but not yet being destructed, in which case
  it seems to do the wrong thing.  Opening a tty that is closing (and
  could be closing for long periods) is supposed to return -EIO.

  I suspect a better way to deal with this and keep the old console
  timing is to split tty->shutdown into two functions.

  tty->shutdown() - called synchronously just before we dump the tty
  onto the waitqueue for destruction

  tty->cleanup() - called when the destructor runs.

  We would then do the shutdown part which can occur in IRQ context
  fine, before queueing the rest of the release (from tty->magic = 0
  ...  the end) to occur asynchronously

  The USB update in -next would then need a call like

       if (tty->cleanup)
               tty->cleanup(tty);

  at the top of the async function and the USB shutdown to be split
  between shutdown and cleanup as the USB resource cleanup and final
  tidy cannot occur synchronously as it needs to sleep.

  In other words the logic becomes

       final kref put
               make object unfindable

       async
               clean it up

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
[ rjw: Rebased on top of 2.6.31-git, reworked the changelog. ]
Signed-off-by: "Rafael J. Wysocki" <rjw@sisk.pl>
[ Changed serial naming to match new rules, dropped tty_shutdown as per
  comments from Alan Stern  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 16 insertions, 13 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index ea18a129b0b..59499ee0fe6 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1389,7 +1389,7 @@ EXPORT_SYMBOL(tty_shutdown);
  *	of ttys that the driver keeps.
  *
  *	This method gets called from a work queue so that the driver private
- *	shutdown ops can sleep (needed for USB at least)
+ *	cleanup ops can sleep (needed for USB at least)
  */
 static void release_one_tty(struct work_struct *work)
 {
@@ -1397,10 +1397,9 @@ static void release_one_tty(struct work_struct *work)
 		container_of(work, struct tty_struct, hangup_work);
 	struct tty_driver *driver = tty->driver;
 
-	if (tty->ops->shutdown)
-		tty->ops->shutdown(tty);
-	else
-		tty_shutdown(tty);
+	if (tty->ops->cleanup)
+		tty->ops->cleanup(tty);
+
 	tty->magic = 0;
 	tty_driver_kref_put(driver);
 	module_put(driver->owner);
@@ -1415,6 +1414,12 @@ static void release_one_tty(struct work_struct *work)
 static void queue_release_one_tty(struct kref *kref)
 {
 	struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
+
+	if (tty->ops->shutdown)
+		tty->ops->shutdown(tty);
+	else
+		tty_shutdown(tty);
+
 	/* The hangup queue is now free so we can reuse it rather than
 	   waste a chunk of memory for each port */
 	INIT_WORK(&tty->hangup_work, release_one_tty);
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index ff75a3589e7..aa6b2ae951a 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -192,7 +192,7 @@ void usb_serial_put(struct usb_serial *serial)
  * This is the first place a new tty gets used.  Hence this is where we
  * acquire references to the usb_serial structure and the driver module,
  * where we store a pointer to the port, and where we do an autoresume.
- * All these actions are reversed in serial_release().
+ * All these actions are reversed in serial_cleanup().
  */
 static int serial_install(struct tty_driver *driver, struct tty_struct *tty)
 {
@@ -339,15 +339,16 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
 }
 
 /**
- * serial_release - free resources post close/hangup
+ * serial_cleanup - free resources post close/hangup
  * @port: port to free up
  *
  * Do the resource freeing and refcount dropping for the port.
  * Avoid freeing the console.
  *
- * Called when the last tty kref is dropped.
+ * Called asynchronously after the last tty kref is dropped,
+ * and the tty layer has already done the tty_shutdown(tty);
  */
-static void serial_release(struct tty_struct *tty)
+static void serial_cleanup(struct tty_struct *tty)
 {
 	struct usb_serial_port *port = tty->driver_data;
 	struct usb_serial *serial;
@@ -361,9 +362,6 @@ static void serial_release(struct tty_struct *tty)
 
 	dbg("%s - port %d", __func__, port->number);
 
-	/* Standard shutdown processing */
-	tty_shutdown(tty);
-
 	tty->driver_data = NULL;
 
 	serial = port->serial;
@@ -1210,7 +1208,7 @@ static const struct tty_operations serial_ops = {
 	.chars_in_buffer =	serial_chars_in_buffer,
 	.tiocmget =		serial_tiocmget,
 	.tiocmset =		serial_tiocmset,
-	.shutdown = 		serial_release,
+	.cleanup = 		serial_cleanup,
 	.install = 		serial_install,
 	.proc_fops =		&serial_proc_fops,
 };